Systems and methods for a subframe structure for wideband LTE

ABSTRACT

System and method embodiments are provided for a subframe structure for wideband LTE. In an embodiment, a method in a communications controller for transmitting a packet to a wireless device includes signaling a UL/DL configuration to the wireless device, wherein the UL/DL configuration indicates a quantity of uplink microframes in a group of microframes, wherein each subframe includes a plurality of microframes, and wherein the group of microframes includes a consecutive sequence downlink microframes and a consecutive sequence of uplink microframes. The packet is transmitted to the wireless device in one downlink microframe. The method further includes receiving an acknowledgement of the packet in an uplink microframe, wherein the uplink microframe is determined in accordance with the one downlink microframe and the uplink-downlink configuration, and wherein the acknowledgement is received in a same subframe as a subframe utilized for transmitting the packet to the wireless device.

This application is a continuation of U.S. patent application Ser. No.15/162,293, filed on May 23, 2016 and entitled “Systems and Methods fora Subframe Structure for Wideband LTE,” which claims priority to U.S.Provisional Application Ser. No. 62/168,152, filed on May 29, 2015entitled “System and Method for a Subframe Structure for Wideband LTE,”both of which applications are hereby incorporated herein by referenceas if reproduced in their entireties.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application is related to U.S. patent application Ser. No.15/162,202, filed May 23, 2016 which is incorporated by reference hereinas if reproduced in its entirety.

TECHNICAL FIELD

The present invention relates to a system and method for wirelesscommunications, and, in particular embodiments, to a system and methodfor a subframe structure for wideband LTE.

BACKGROUND

The current spectrum allocation for cellular systems is becominginadequate in capacity as the number of users and volume of trafficincreases. To increase the amount of spectrum available for cellularusage, the cellular industry (e.g., operators, system manufacturers, anddevice manufacturers) are targeting newer frequency bands. Thesefrequency bands are higher in frequency (e.g., 3.5 GHz-6 GHz) than thetraditional cellular bands (e.g., 700 MHz to 2.5 GHz), typically largerin contiguous bandwidth (e.g., up to 400 MHz) compared to the typicalmaximum of 20 MHz, and most likely unpaired (only one band is availablefor transmission and reception).

SUMMARY

An embodiment method in a communications controller for transmitting apacket to a wireless device includes signaling, by the communicationscontroller, an uplink/downlink (UL/DL) configuration to the wirelessdevice, wherein the UL/DL configuration indicates a quantity of uplinkmicroframes in a group of microframes, wherein each subframe includes aplurality of microframes, and wherein the group of microframes includesa consecutive sequence downlink microframes and a consecutive sequenceof uplink microframes. The method also includes transmitting, by thecommunications controller, the packet to the wireless device in onedownlink microframe of the consecutive sequence of downlink microframes.The method further includes receiving, by the communications controller,an acknowledgement of the packet in an uplink microframe, wherein theuplink microframe is determined in accordance with the one downlinkmicroframe and the uplink-downlink configuration, and wherein theacknowledgement is received in a same subframe as a subframe utilizedfor transmitting the packet to the wireless device.

In an embodiment, the consecutive sequence of downlink microframesincludes a special microframe, and wherein the special microframeincludes at least one downlink symbol and a guard period. In anembodiment, the uplink microframes are further determined in accordancewith a next uplink-downlink configuration of a next group ofmicroframes. In an embodiment, a subframe is divided into eightmicroframes, wherein K first microframes are UL. In an embodiment, aplurality of subframes comprise a supermicroframe, wherein a K firstmicroframes in a first subframe are DL microframes and a firstmicroframe in each of the subsequent subframes are a DL microframe or anUL microframe. In an embodiment, the method also includes signaling theUL/DL configuration using a physical control format indicator channel(PCFICH)-like channel. In an embodiment, signaling the UL/DLconfiguration using a physical control format indicator channel(PCFICH)-like channel includes sending the PCFICH-like channel on atleast one reserved resource element (RE) in a first microframe of afirst subframe. In an embodiment, the method includes explicitlysignaling a subframe in which to send an acknowledgement/negativeacknowledgement (ACK/NAK). In an embodiment, the explicit signalingincludes one bit indicating whether to send the ACK/NACK using animplicit rule or a pre-determined microframe.

An embodiment communications controller includes a processor and anon-transitory computer readable storage medium storing programming forexecution by the processor. The programming includes instructions forsignaling an uplink/downlink (UL/DL) configuration to the wirelessdevice, wherein the UL/DL configuration indicates a quantity of uplinkmicroframes in a group of microframes. Each subframe includes aplurality of microframes. The group of microframes includes aconsecutive sequence downlink microframes and a consecutive sequence ofuplink microframes. The programming also includes instructions fortransmitting the packet to the wireless device in one downlinkmicroframe of the consecutive sequence of downlink microframes. Theprogramming further includes instructions for receiving anacknowledgement of the packet in an uplink microframe. The uplinkmicroframe is determined in accordance with the one downlink microframeand the uplink-downlink configuration. The acknowledgement is receivedin a same subframe as a subframe utilized for transmitting the packet tothe wireless device.

An embodiment method in a wireless device for communicating with acommunications controller includes receiving, by the wireless device, anuplink/downlink (UL/DL) configuration from the communicationscontroller. The UL/DL configuration indicates a quantity of uplinkmicroframes in a group of microframes. Each subframe includes aplurality of microframes. The group of microframes includes aconsecutive sequence downlink microframes and a consecutive sequence ofuplink microframes. The method also includes receiving, by the wirelessdevice, a packet from the communications controller in one downlinkmicroframe of the consecutive sequence of downlink microframes. Themethod further includes transmitting, by the wireless device, anacknowledgement of the packet in an uplink microframe. The uplinkmicroframe is determined in accordance with the one downlink microframeand the uplink-downlink configuration. The acknowledgement istransmitted in a same subframe as a subframe utilized for receiving thepacket from the communications controller.

In an embodiment, the consecutive sequence of downlink microframesincludes a special microframe, and wherein the special microframeincludes at least one downlink symbol and a guard period. In anembodiment, the uplink microframes are further determined in accordancewith a next uplink-downlink configuration of a next group ofmicroframes. In an embodiment, a subframe is divided into eightmicroframes, wherein K first microframes are UL. In an embodiment, aplurality of subframes comprise a supermicroframe, wherein a K firstmicroframes in a first subframe are DL microframes and a firstmicroframe in each of the subsequent subframes are a DL microframe or anUL microframe.

An embodiment wireless device includes a processor and a non-transitorycomputer readable storage medium storing programming for execution bythe processor. The programming includes instructions for receiving anuplink/downlink (UL/DL) configuration from the communicationscontroller. The UL/DL configuration indicates a quantity of uplinkmicroframes in a group of microframes. Each subframe includes aplurality of microframes. The group of microframes includes aconsecutive sequence of downlink microframes and a consecutive sequenceof uplink microframes. The programming also includes instructions forreceiving a packet from the communications controller in one downlinkmicroframe of the consecutive sequence of downlink microframes. Theprogramming also includes transmitting an acknowledgement of the packetin an uplink microframe. The uplink microframe is determined inaccordance with the one downlink microframe and the uplink-downlinkconfiguration. The acknowledgement is transmitted in a same subframe asa subframe utilized for receiving the packet from the communicationscontroller.

In various embodiments, simpler ACK/NAK timing rules are provided ascompared against legacy TDD design for LTE. Embodiments provide for lowlatency and dynamic downlink/uplink configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates an embodiment of a microframe;

FIG. 2 illustrates an embodiment of a microframe fitting in the LTEnumerology;

FIG. 3 illustrates an embodiment of microframes for FDD;

FIG. 4 illustrates an embodiment of DL scheduling;

FIG. 5 illustrates embodiments of uplink-downlink configurations;

FIG. 6 illustrates an embodiment of signaling of uplink-downlinkconfiguration;

FIG. 7 illustrates an embodiment of a guard period in a specialmicroframe;

FIG. 8 illustrates embodiments of possible uplink-downlinkconfigurations;

FIG. 9 illustrates a embodiment of a supermicroframe configuration;

FIG. 10 illustrates a first embodiment of UL scheduling;

FIG. 11 illustrates a second embodiment of UL scheduling;

FIG. 12 illustrates a third embodiment of UL scheduling;

FIG. 13 illustrates an embodiment of DL HARQ timing;

FIG. 14 illustrates an embodiment method in an eNB for HARQ-ACK flow;

FIG. 15 illustrates an embodiment method in a UE for HARQ-ACK flow;

FIG. 16 illustrates an embodiment of UL HARQ timing;

FIG. 17 illustrates a block diagram of an embodiment processing systemfor performing methods described herein;

FIG. 18 illustrates a block diagram of an embodiment transceiver adaptedto transmit and receive signaling over a telecommunications network; and

FIG. 19 illustrates an embodiment network for communicating data inwhich the disclosed methods and systems may be implemented

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The structure, manufacture and use of the presently preferredembodiments are discussed in detail below. It should be appreciated,however, that the present invention provides many applicable inventiveconcepts that can be embodied in a wide variety of specific contexts.The specific embodiments discussed are merely illustrative of specificways to make and use the invention, and do not limit the scope of theinvention.

In order to operate at higher frequencies and wider bandwidths, thecellular industry has several options. One option is to use carrieraggregation (CA) to enable multiple 20 MHz carriers to fill theavailable bandwidths. Another option is enhance the physical layer ofLong Term Evolution (LTE) to operate with larger bandwidths. While thefirst option is attractive by just changing the carrier frequency to thehigher frequencies, it maintains the design features and accompanyingissues of the current LTE system (latency, overhead). The second optionwould need changes but allows design for lower latency, reducedoverhead, and higher throughput.

Legacy time division duplexing (TDD) design for LTE has a number ofshortcomings. First, LTE TDD was designed after LTE frequency divisionduplexing (FDD). The legacy LTE TDD design includes seven subframeconfigurations. Subframe (SF) 2 is always an UL subframe. SFs 0 and 5are always downlink (DL) SFs. SF 1 is always a special SF. SF 6 can beeither a DL SF or a special SF

An additional benefit provided by developing wideband LTE is a reductionin the current LTE latency. The current LTE subframe structure is notsuitable to achieve the latencies typically considered for fifthgeneration (5G) systems (e.g., 1 ms). Therefore, there is a need for anew subframe structure for wideband LTE.

An embodiment method for transmitting a packet to a wireless deviceincludes signaling, by a communications controller, an uplink/downlink(UL/DL) configuration to the wireless device, wherein the UL/DLconfiguration indicates a quantity of uplink microframes in a group ofmicroframes. The group of microframes includes a consecutive sequencedownlink microframes and a consecutive sequence of uplink microframes.The method also includes transmitting, by the communications controller,the packet to the wireless device in one downlink microframe of theconsecutive sequence of downlink microframes. Additionally, the methodincludes receiving, by the communications controller, an acknowledgementof the packet in an uplink microframe. The uplink microframe isdetermined in accordance with the one downlink microframe and theuplink-downlink configuration. In an embodiment, the consecutivesequence of downlink microframes includes a special microframe, andwherein the special microframe includes downlink symbols and a guardperiod. In an embodiment, the uplink microframe is further determined inaccordance with a next uplink-downlink configuration of a next group ofmicroframes. In an embodiment, the quantity of uplink microframes isrelated to the consecutive sequence of uplink microframes. In anembodiment, a subframe is divided into eight microframes, wherein Kfirst microframes are UL, and wherein a supermicroframe includes a firstsubframe having K first microframes being DL, and subsequent subframesafter the first subframe have the K first microframes being UL or DL. Inan embodiment, the method also includes signaling the UL/DLconfiguration using a physical control format indicator channel(PCFICH)-like channel sent on reserved resource elements (REs) inmicroframe 0 of subframe 0. In an embodiment, the method also includesexplicitly signaling of a subframe in which to send anacknowledgement/negative acknowledgement (ACK/NAK). In an embodiment,the explicit signaling includes one bit indicating whether to send theACK/NACK using an implicit rule or a pre-determined microframe.

An embodiment communications controller includes a processor and anon-transitory computer readable storage medium storing programming forexecution by the processor. The programming includes instructions forsignaling an uplink/downlink (UL/DL) configuration to a wireless device.The UL/DL configuration indicates a quantity of uplink microframes in agroup of microframes. The group of microframes includes a consecutivesequence downlink microframes and a consecutive sequence of uplinkmicroframes. The programming also includes instructions for transmittinga packet to the wireless device in one downlink microframe of theconsecutive sequence of downlink microframes. The programming alsoincludes instructions for receiving an acknowledgement of the packet inan uplink microframe, wherein the uplink microframe is determined inaccordance with the one downlink microframe and the uplink-downlinkconfiguration.

One aspect of overhead is dynamic frame configuration switching. InRelease 12 specifications of LTE (Rel-12), there are features that allowthe uplink-downlink configuration for time division duplexing (TDD) mode(frame structure type 2) to change every 10 ms. Before the introductionof dynamic switching of the uplink-downlink configuration (e.g.,enhanced interference management and traffic adaptation (eIMTA)), theconfiguration was chosen from one option in Table 1 (from Table 4.2-2 of3GPP 36.211).

TABLE 1 Uplink-downlink configuration Uplink-downlink configuration 0 12 3 4 5 6 7 8 9 0 D S U U U D S U U U 1 D S U U D D S U U D 2 D S U D DD S U D D 3 D S U U U D D D D D 4 D S U U D D D D D D 5 D S U D D D D DD D 6 D S U U U D S U U D

In Table 1, “D” represents a downlink (DL) subframe, “U” represents anuplink (UL) subframe, and “S” represents a special subframe. In LTE, asubframe is defined as 30,720 samples where the sample rate (1/Ts) is30,720,000 samples/sec. In the special subframe, the samples are groupedinto three sets. The first set of samples forms the downlink pilottimeslot (DwPTS), the second set of samples forms the guard period (G),and the last set forms the uplink pilot timeslot (UpPTS). The number ofsamples in each set is defined by the standards. The guard period allowsthe device to switch from receiving downlink transmissions totransmitting uplink transmissions as well as allowing timing advance.

With eIMTA, one or more capable UEs would monitor downlink controlindicator (DCI) format IC to determine the uplink-downlink configurationfor the next radio frame (one radio frame is 10 subframes, where thesubframes are numbered 0 to 9). DCI format IC is transmitted on thephysical downlink control channel (PDCCH) using the common search spacerules. There are certain uplink-downlink configurations could be groupedtogether, such as ((4, 0, 1, 3, 6), (5, 0, 1, 2, 3, 6), (2, 0, 1, 6)).

Among the considerations in the grouping for eIMTA is how theacknowledgements and negative acknowledgements (ACK/NACK or A/N) for thereception of packets are transmitted. In general, certainacknowledgements and negative acknowledgements indicators for hybridautomatic repeat request (HARQ) processes are transmitted as HARQ-ACKbits in the uplink control information (UCI) sent on the physical uplinkcontrol channel (PUCCH). For example, a UE receiving a downlinktransmission in subframe n would sent HARQ-ACK bits on an uplinksubframe. For frequency division duplexing (FDD), the HARQ-ACK bits aretransmitted in subframe n+4 (if the sum is less than 10, subframe n+4 inthe current frame is used, otherwise subframe n+4-10 in the next frameis used). For TDD, the transmission of HARQ-ACK bits is a function ofsubframe number and the uplink-downlink configuration and is at least 4subframes later. For eIMTA, a different function based on the currentsubframe number, the future uplink-downlink configuration, and currentuplink-downlink configuration may be needed.

In the enhanced wide bandwidth LTE system, a desired feature is toenable low latency. Embodiments described below provide a microframestructure to enable low latency.

FIG. 1 is a diagram illustrating an embodiment subframe system 100. Eachsubframe 101 is divided into several microframes 102, as shown inFIG. 1. In this example, there are 8 microframes 102 (labeled 0, 1, 2, .. . , 7) in one subframe. In an embodiment, the duration of eachmicroframe 102 is 125 microseconds (μs). The microframe 102 can beconfigured for either uplink or downlink transmission. For TDD, aspecial microframe may be defined and capable of supporting uplink anddownlink transmissions. Another type of a special microframe has adownlink portion and guard period. There can be a PDCCH or enhancedPDCCH (EPDCCH) in each downlink microframe and special microframe forTDD. Each microframe 102 contains one or more orthogonal frequencydivision multiplex (OFDM) symbols 103. In the frequency domain, eachOFDM symbol 103 includes resource elements (subcarriers). The subcarrierspacing (frequency separation between adjacent subcarriers) can be 60kHz. In the time domain, each OFDM symbol 103 has a cyclic prefix (CP)field 104 with n_(CP) samples. Each symbol 103 of the microframe 102 canhave a different value for n_(CP). In many realizations, the OFDM symbol103 in the time domain can be generated by performing an inverse fastFourier transform (IFFT) on the subcarriers. The last n_(CP) samples ofthe IFFT output 105 can be used for the cyclic prefix.

Note that with Rel-12 LTE, a subframe 101 is divided into two 0.5 msslots. One difference between a microframe 102 and a slot is thelocation of the control channel. With slots, the PDCCH is located onslot 0 and the EPDCCH spans both slots of the subframe.

Also note that in some embodiment of the disclosed systems and methods,the subframe duration and radio frame are untouched. In an embodiment,the subframe duration is 1 ms, 10 subframes make up a radioframe, etc.

FIG. 2 is a diagram illustrating an embodiment of theradioframe/subframe/microframe division 200. In an embodiment, eachradio frame is about 10 milliseconds (ms) in duration. Each radio frame202 includes ten subframes 204 of 1 ms each. Each subframe 204 includeseight microframes 206 of 0.125 ms each. Each microframe 206 includes aplurality of symbols 208 where each symbol is about 16.66 μs.

An embodiment numerology is given as an example in Table 2, where 1/Ts'is 16×(1/Ts) with 1/Ts=30,720,000 samples/sec.

TABLE 2 Example of numerology. Number of Unit Duration Relationship Ts′samples Frame 10 ms 4915200 Subframe 1 ms 10 subframes/frame 491520Microframe 0.125 ms 8 microframes/subframe 61440 Symbol 16.66 μs 8192(no CP)

With respect to the cyclic prefix, with a 60 kHz subcarrier spacing, thenumber of tones (subcarriers) in one OFDM symbol is 1/Ts′/60,000=8192.The number of samples in a 1 ms subframe is 1/Ts′/1000=491520 (60 OFDMsymbols). To determine the number of symbols in a microframe and theamount of overhead, one possible procedure is to evaluate an equationN _(sym) ^(SF) =N _(sym) ^(CP) +N _(sym) ^(mf) N _(mf)  (1)where N_(sym) ^(SF)=60 is the number of OFDM symbols in a subframe (SF),N_(sym) ^(CP) is the number of OFDM symbols that will be reserved foroverhead (cyclic prefix (CP)), N_(sym) ^(mf) is the number of symbols ina microframe, and N_(mf) is the number of microframes in a subframe. Thesamples of the overhead symbols will be distributed among the N_(sym)^(mf)N_(mf) symbols, thereby providing those symbols with a cyclicprefix. From a design perspective,

-   -   the value of N_(sym) ^(CP) can be used to determine cell        coverage and possible deployments,    -   the value of N_(sym) ^(mf) can be used to determine the amount        of data that can be conveyed in a microframe, and    -   the value of N_(mf) can be used to determine latency.

The average CP duration in terms of time isτ_(sym) N _(sym) ^(CP)/(N _(mf) N _(sym) ^(mf)),  (2)where τ_(sym) is the duration of one OFDM symbol (16.66 μs). The actualCP duration may deviate from the average CP duration due to using aninteger number of samples per symbol.

Three possible microframe configurations that satisfy (1) are listed inTable 3.

TABLE 3 Microframe configurations Mode N_(sym) ^(CP) N_(sym) ^(mf)N_(mf) Average CP duration, μs 1  4 7 8 1.19 2 12 6 8 4.16 3 20 5 8 8.33

As indicated by Table 3, mode 1 has 7 ODFM symbols/microframe and 8microframes per subframe.

To determine the actual number of samples allocated to the CP for eachsymbol of the microframe, one possible procedure is to solve(N _(sym) ^(CP) /N _(mf))N _(samp) ^(sym)=(N _(sym) ^(mf)−x)aQ+x(a+1)Q  (3)where N_(samp) ^(sym) is the number of samples in an OFDM symbol (8192),a is an integer to be determined, Q is a granularity (such as 32) suchthat aQτ_(sym)≤τ_(sym)N_(sym) ^(CP)/(N_(sym) ^(mf)N_(mf))≤(a+1)Qτ_(sym),and x is the number of microframes with a larger CP (i.e., (a+1)Q) andN_(sym) ^(mf)−x is the number of microframes with a shorter CP (i.e.,aQ).

TABLE 4 Example of CP allocation. Q = 32, sample duration = Ts′ LongerCP, #microframe, Shorter CP, #microframe, #samples Mode shorter CP#samples (aQ) longer CP ((a + 1)Q) 1 5  576 2 608 2 6 2048 3 5 4096

Table 4 indicates that in mode 1, there are 7 symbols in a microframe. 5symbols will have a CP of 576 samples (1/Ts′) while 2 symbols will havea CP of 608 samples. The average CP duration is 1.19 μs. There can be

$\frac{N_{sym}^{mf}!}{{\left( {N_{sym}^{mf} - x} \right)!}\mspace{14mu}{x!}}$possible symbol arrangements, where N_(sym) ^(mf)=7 is the number ofsymbols in a microframe, and x=2 is the number of symbols with a longerCP. One example of an arrangement is having the first and last symbolsof the microframe use a longer CP. The choice of an arrangement can bemade based on performance.

The general microframe structure described above can be applied to FDD.

FIG. 3 is a diagram illustrating an embodiment of the disclosedmicroframe structure 300 as applied to FDD, showing downlink microframes302 and uplink microframes 304. An example of an n+3 rule is used fordata transmission on both the uplink and downlink. For the transmissionof data on the uplink in microframe 3 (solid line) by the UE, the eNBtransmits an uplink grant (DCI) in microframe 0 (dashed line). Fordownlink data transmission, the eNB transmits a downlink assignment(DCI) as well as data in microframe 6. In microframe 1 (microframe n+3),the UE transmits the acknowledgement bits.

FIG. 4 illustrates an embodiment of DL scheduling 400. With respect toDL scheduling 400, FIG. 4 shows an example of EPDCCH 402 for signalingof data in the same microframe and PDCCH 404 (occupying the firstsymbols of downlink (special) microframe, such as microframe 0) withrespect to DL scheduling. The EPDCCH could span the DL microframe (ordownlink portion of a special microframe). The (E)PDCCH can be used toschedule uplink grants for data and possibly other operations that mayrequire uplink transmissions (e.g., measurement reporting).

With respect to TDD, in an embodiment, the microframe structure allowsdynamic uplink-downlink configuration without having complicated rulesfor configurations or complicated rules for transmitting HARQ-ACK bitswhile ensuring low latency. The following discussion describes severalsuch approaches.

For signaling, to support a dynamic uplink-downlink configuration, thesubframe can be partitioned into a set of consecutive downlinkmicroframes followed by a set of consecutive uplink microframes. Theremay be a special microframe between the downlink microframe and uplinkmicroframe. If N_(mf) denotes the number of microframes in a subframe(e.g., 8), N_(mf) ^(DL) denotes the number of downlink microframes, andN_(mf) ^(SP) is the number of special microframes in a subframe, thenthe number of uplink microframes in a subframe, N_(mf) ^(UL), can beexpressed as N_(mf) ^(UL)=N_(mf)−N_(mf) ^(DL)−N_(mf) ^(SP). As a result,when the number of microframes in a subframe is known (e.g.,standardized or signaled through other physical layer means or by higherlayer messaging), only the number of downlink microframes in a subframeneeds to be signaled. The number of special microframes is typically 1.More specifically, in an embodiment, the subframe configuration is asfollows:

-   -   Microframes #0, . . . , N_(mf) ^(DL)−1 are configured as        downlink microframes,    -   Microframes # N_(mf) ^(DL)+N_(mf) ^(SP), . . . , N_(mf)−1 are        configured as uplink microframes, and    -   Microframe N_(mf) ^(DL), . . . , N_(mf) ^(DL)+N_(mf) ^(SP)−1 may        be designated as the special microframe.

In an embodiment, one possible requirement is having at least one uplinkmicroframe and at least one downlink/special microframe in a subframe,i.e., N_(mf) ^(UL)>0 and N_(mf) ^(DL)+N_(mf) ^(SP)>0.

FIG. 5 illustrates embodiments of uplink-downlink configurations 500.FIG. 5 shows 7 possible uplink-downlink configurations 500. Throughoutthis disclosure, a dotted box indicates a downlink microframe (e.g.,microframe 0 in configuration 6 in FIG. 5), a cross-hatched boxindicates a special microframe (e.g., microframe 0 in configuration 9 inFIG. 5), and a diagonal striped box indicates an uplink microframe(e.g., microframe 1 in configuration 0 of FIG. 5). The specialmicroframe may have a guard period to facilitate Rx/Tx switching. As aresult, the special microframe can have fewer data-bearing symbols(hence lower data rate). The special microframe precedes the firstuplink microframe in a group of consecutive uplink microframes. Note asimilar mapping can be based on the number of uplink microframes. Notethat with these set of configurations, microframe#0 is DL or special,and microframe #7 is UL. With the partitioned subframe (consecutivedownlink microframes followed by a special microframe followed byconsecutive uplink microframes), the uplink-downlink configuration canalso indicate the number of downlink microframes of each subframe or thelocation of the special microframe for each subframe.

The microframe configuration needs to be signaled to the UE. There areseveral possible ways of signaling. First, if the uplink-downlinkconfiguration does not change very often, it could be communicated byradio resource configuration (RRC) signaling, either dedicated(UE-specific) or common (broadcast). In the extreme case, theuplink-downlink configuration could be signaled using the masterinformation block (MIB) transmitted in the physical broadcast channel(PBCH).

Second, a channel similar to the physical control format indicatorchannel (PCFICH) can be used to indicate the uplink-downlinkconfiguration. This similar channel could be sent on reserved resourceson dedicated microframes (e.g., microframe #0 of the subframe,microframe #0 of subframe #0, etc.). In this example, the signaling canbe sent every 1 ms. A slower rate can be used.

Third, the signaling could be done by using sequences.

Fourth, the signaling could also be done by using a special DCI.

With respect to sequence signaling, in microframe 0, there can be a setof waveforms transmitted by the eNB that indicate the uplink-downlinkconfiguration. One example is to select a waveform from a set ofwaveforms indexed by the uplink-downlink configuration Table 5 shows anexample of a mapping between the configuration and bit pattern.

TABLE 5 Bit sequence indicating uplink-downlink configurationUplink-downlink configuration Bit pattern 0 0000 0000 0000 0000 00000000 0000 0000 1 1100 1100 1100 1100 1100 1100 1100 1100 2 0011 00110011 0011 0011 0011 0011 0011 3 1001 1001 1001 1001 1001 1001 0101 01014 1010 1010 1010 1010 1010 1010 1010 1010 5 0101 0101 0101 0101 01010101 0101 0101 6 0110 0110 0110 0110 0110 0110 0110 0110 7 1111 11111111 1111 1111 1111 1111 1111

Once a bit pattern is selected based on the uplink-downlinkconfiguration, it can be mapped into a sequence of quadrature phaseshift key (QPSK) points, such as 00→exp(jπ/4), 01→exp(−jπ/4),10→exp(j3π/4), 11→exp(−j3π/4), where j=sqrt(−1). Let φ_(i) denote thesequence associated with uplink-downlink configuration i, i=0, . . . ,6. The bit pattern can be chosen so that the sequences φ_(i) have goodcross-correlation properties, such as

$\begin{matrix}{{\varphi_{i}^{*}\varphi_{k}} = \left\{ \begin{matrix}{N,} & {{i = k},} \\{0,} & {{i \neq k},}\end{matrix} \right.} & (4)\end{matrix}$where “*” denotes Hermitian transpose, and N is the length of thesequence φ_(i). This sequence can be transmitted in microframe 0 (thefirst microframe of each subframe).

FIG. 6 (waveform) shows the location of the sequence in the frequencydomain in an embodiment. In this example, the waveform 602 is located onnon-adjacent subcarriers of the first OFDM symbol of microframe 0 600.In general, the waveform 602 can be located on any of the OFDM symbolsof a microframe. In general, the subcarriers can be non-adjacent,adjacent or groups of adjacent subcarriers. Note also that the sequencecan be used to color another signal, such as Reference Signal (RS).

With respect to signaling using a special DCI format, an embodiment usesa DCI that all UEs can process. The uplink-downlink configuration isconveyed by that DCI.

FIG. 6 (control) shows an example of the DCI 604 placed (logically) inan EPDCCH that spans the symbols of microframe 0 600 in an embodiment.This DCI 604 can be placed in a common search space.

Note that for TDD system operations, the network needs to synchronize atthe microframe level to avoid strong UL/DL interference from neighboringcells. If a dynamic microframe configuration is deployed, the networkmay need very short delay backhaul to communicate dynamic microframeconfiguration at the subframe level.

Another type of DCI (or field within a DCI) that can augment operationis a probe DCI. For brevity, the term “probe field” is used. One purposeis to signal a UE when to receive scheduling DCIs. In one application,the probe field is transmitted in microframe 0 when it is configured asa downlink or special microframe. In one example, the size of the probefield is related to the number of microframes in a subframe. With 8microframes in a subframe, the bit field can be 7 bits. Because a UE isreceiving this field, a bit is not needed. In example A in Table 6, thefield “0101000” can indicate to a UE to expect DCIs in microframes 2 and4 (indicated by “1”) in the field. The bit position in the field isrelated to the microframe number. The most significant bit can map tomicroframe 1. On the microframes where the UE is no “1” assigned, the UEmay decide not to receive DCI (as a possible power savings feature).

In example B in Table 6, the field “1000100” can indicate to a UE toexpect DCI in microframe 1. When coupled with the uplink-downlinkconfiguration, the bits that are allocated for uplink microframes can beused to indicate when HARQ-ACK bits are transmitted. Typically there arerules, such as described below with respect to DL HARQ, when a UEtransmits the HARQ-ACK bits but this may complement those rules. In thisexample, microframe 5 is used by the UE to transmit the HARQ-ACK bitsfor a received packet in microframe 1.

TABLE 6 Probe field example (columns “1”, . . . , “7” indicatemicroframe number) Ex- ample 1 2 3 4 5 6 7 Description A 0 1 0 1 0 0 0Expect DCI in microframes 2 and 4 (indicated by 1) B 1 0 0 0 1 0 0Expect DCI in microframe 1. Transmit A/N in microframe 5

There may be a DCI which packs the probe fields together (consider anarray of p fields each with a size P=7 bits. A UE may be assigned anindex i∈{0, . . . , p−1} during a configuration. The UE examines bits iPto (i+1)P−1 for its probe field. Multiple UEs may be assigned the sameindex.

For a TDD deployment, the transitions between downlink and uplink aswell as uplink and downlink need a guard time s in order to allow thehardware to switch functionalities. With respect to a specialmicroframe, in LTE Rel-12, the special subframe has a guard period thatincorporates the switch times and adds a margin of time for timingadvance. A UE uses timing advance to adjust its transmit timing.Typically, the amount of timing advance is proportional to the distancebetween the eNB and UE. For line-of-sight communications, an estimate oftiming advance is 2d/c, where d is the distance and c is the speed oflight.

The amount of guard period can be expressed as 2s+2d/c.

TABLE 7 Guard periods d s 100 m 200 m 500 m 1000 m 200 m 10 μs 20.7 21.323.3 26.7 33.3 12 μs 24.7 25.3 27.3 30.7 37.3 14 μs 28.7 29.3 31.3 34.741.3 16 μs 32.7 33.3 35.3 38.7 45.3

One design option is to select the duration of the guard period as amultiple of the OFDM symbol and cyclic prefix. For example, for mode 1,a CP of 576 samples is about 1.17 μs. Thus one OFDM symbol with this CPis 17.84 μs. Multiples (in μs) include 35.68, 53.52, 71.36. One possiblechoice for s is 14 μs and d is 1000 m. If a smaller switch time isallowed, then the distance can increase.

Each mode can select the appropriate number of symbols to use to accountfor a larger coverage area.

FIG. 7 illustrates one embodiment of a special microframe 704 foruplink-downlink configuration 1 (defined in FIG. 5) and mode 1. Eachsubframe 702 includes eight microframes labeled 0, 1, 2, . . . , 7. Themicroframe labeled “1 ” is a special microframe 704. In the specialmicroframe 704, the first 5 symbols 706 (dotted) are configured for DL.The last two symbols 708 (solid) are for the guard. In the subframe 702,a dotted microframe is a DL microframe, a diagonal hashed microframe isa UL microframe, and horizontal/vertical lines in a microframe indicatesa special microframe 704. The eNB may signal the special microframeconfiguration.

FIG. 8 illustrates embodiments of possible uplink-downlinkconfigurations 800. The configurations 800 are labeled 13, 12, 11, . . ., 7. With respect to a supermicroframe pattern, the subframe can bepartitioned into a set of uplink microframes followed by a set ofdownlink microframes as illustrated in FIG. 8, where possibleuplink-downlink configurations with a dotted box indicating a downlinkmicroframe, a cross-hatched box indicating a special microframe, and thediagonal striped box indicating an uplink microframe. The specialmicroframe may have a guard period to facilitate Rx/Tx switching. As aresult, the special microframe can have data-bearing fewer symbols(hence lower data rate). The special microframe precedes the firstuplink microframe in a group of consecutive uplink microframes. Thespecial microframe in uplink-downlink configurations 7-13 may beoptional in a subframe when the next subframe uses uplink-downlinkconfigurations 0-6. Note that a different special microframe with guardfollowed by data-bearing symbols (for the DL) can be defined. With thisdifferent special microframe, the first microframe after the last uplinkmicroframe could be this special microframe.

A supermicroframe pattern includes multiple subframes, where the firstsubframe includes one of the configuration 0-7, and the subsequentsubframes include any of the configurations 0-13.

FIG. 9 illustrates a embodiment of a supermicroframe configuration 900,where a super microframe structure 900 consists of 3 subframes 902, 904,906. In an embodiment, a supermicroframe 900 may be used to reducelatency due to delays in HARQ-ACK bit transmissions. FIG. 9 illustratesan example where the HARQ-ACK bits of 2 microframes are bundled. It isassumed that HARQ-ACK bundling is not used for the special microframe.The first microframe of subframe 1 is an UL microframe, and the HARQ-ACKfeedback for microframes 3 and 4 of subframe 0 can be sent in thatmicroframe, hence reducing latency.

With respect to UL scheduling, scheduling traffic on the uplink impliesthe eNB sends DCIs for uplink grants on the downlink/special portions ofthe subframe.

FIG. 10 illustrates a first embodiment of UL scheduling 1000. In theexample shown in FIG. 10, the subframe 1002 in configuration 1 has twodownlink microframes 1004, 1006 (labeled “0” and “1”) and 6 uplinkmicroframes 1008, 1010, 1012, 1014, 1016, 1018 (labeled “2”, “3”, “4”,“5”, “6”, and “7”). When the special microframe has only downlink andguard, it can be considered as a downlink microframe. In microframe 01004, there are 3 uplink grants, DCI A0, DCI A1, and DCI A2, for data A0in microframe 2 1008, data A1 in microframe 3 1010, and data A2 inmicroframe 4 1012, respectively. Likewise in microframe 1 1006, thereare 3 uplink grants, DCI B0, DCI B1, and DCI B2, for data B0 inmicroframe 5 1014, data B1 in microframe 6 1016, and data B2 inmicroframe 7 1018, respectively. In an embodiment, there is a minimum 2microframe delay between the transmission of the grant and thetransmission of the data. A minimum rule such as n+2 can be used,allowing a UE to prepare for data transmission after receiving a grant.

FIG. 11 illustrates a second embodiment of UL scheduling 1100. In theexample shown in FIG. 11, configuration 1 is used again. The subframe1102 includes eight microframes 1104, 1106, 1108, 1110, 1112, 1114,1116, 1118 (labeled “0”, “1”, “2”, “3”, “4”, “5”, “6”, and “7”). Inmicroframe 1 1106, there are 5 uplink grants, DCI C0, DCI C1, DCI C2,DCI C3, and DCI C4, for data C0 in microframe 2, data C1 in microframe 31110, data C2 in microframe 5 1114, data C3 in microframe 6 1116, anddata C4 in microframe 7 1118, respectively. In this example, the lastdownlink microframe 1106 is used for scheduling uplink traffic. In anembodiment, all grants are sent in this last DL microframe 1106. In anembodiment, the scheduling of DCI C0 in DL1 for UL2 assumes the UE canimplement an n+1 rule for uplink traffic. It may be possible given thatthere is some guard period (DL1 is a special microframe). Typically, ann+2 rule may be preferred.

FIG. 12 illustrates a third embodiment of UL scheduling 1200. Fiveconfigurations are illustrated in FIG. 12. Thus, another example forscheduling may allow uplink-downlink configurations with at least twouplink microframes and at least two downlink microframes (one microframeis designated as a special microframe), as shown in FIG. 12. Then arule, such as minimum of 2 microframes, can be used and the lastdownlink microframe is used to schedule uplink microframes that are morethan 2 microframes later (see configuration 4 where DL microframe 4 isused to schedule DL microframes 6 and 7, for example).

The following provides embodiments of DCI formats that may be needed tosupport this signaling.

A simple way to accommodate the signaling needed for signaling suchconfigurations is to always include 3 bits indicating to whichmicroframe index the DCI applies. The index applies either to thecurrent subframe or to the next microframe. However, there are possibleoptimizations.

Case 1, more DL microframes than UL microframes: in such a case, thereis no ambiguity for the UL signaling. The UL signaling is valid for theUL microframe after a fixed number of microframes (e.g., 2 or 4). Thisis what is done for LTE.

Case 2, more UL microframes than DL microframes: in such a case,multi-microframe scheduling is needed to be able to address all ULmicroframes. This can be done by adding the microframe index for whichthe addressing is valid (added in this case only).

Case 3, special UL assignment: latency reduction is one of the primarygoals for WB-LTE. It might then be worth to assign the UL on aparticular microframe, for instance the last microframe of the subframe.In such a case, one bit could be added. If this bit is set to aparticular value (or toggled), the DCI assignment follows the e.g., n+2rule. If it has the other value, the DCI is for a pre-determinedmicroframe (or configured by e.g., RRC signaling).

The HARQ timing, which incorporates data transmissions, acknowledgmenttransmission, and re-transmission, is determined to ensure low latency.In Rel-12, the general rule for FDD is if a packet were transmitted insubframe n, the acknowledgment is transmitted in subframe n+4, and thedata can be re-transmitted in subframe n+8. The general rules for TDDare more complex where the acknowledgement and retransmission are sentin subframe n+k and subframe n+k+l, respectively, where k≥4 and l≥4, andthe values of k and l are a function of the subframe number n anduplink-downlink configuration.

For DL HARQ and microframe structures, an example of an n+2 rule isshown in Table 8. The goal is for a UE to send its HARQ-ACK bits for apacket in the second microframe after receiving the packet. Due to thepartitioned subframe structure, for some uplink-downlink configurations,there are some exceptions for the n+2 rule. For example, uplink-downlinkconfiguration 6, the HARQ-ACK bits for a packet received in microframe 6will be in the next subframe (as indicated by the “*” in the table).Details on when a UE can send the HARQ-ACK bits in this example arepresented below with respect to the n+2 rule, restricted uplink-downlinkconfigurations.

For certain uplink-downlink configurations (#4, #5, #6), techniques suchas bundling and multiplexing may be needed (described with respect tothe n+2 rule, restricted uplink-downlink configurations). With the n+2rule, the earliest HARQ-ACK bits can be transmitted by the UE forpackets in downlink microframes 0, 1, 2, 3 is microframe 5. HARQ-ACKbits for microframe 4 can be transmitted in microframe 6. What ispresented in the table is HARQ-ACK bits for microframes 0 and 1 are sentin microframe 5; HARQ-ACK bits for microframes 2 and 3 are sent inmicroframe 6; and HARQ-ACK bits for microframe 4 is sent in microframe7. One reason is to distribute uplink transmissions across all uplinkmicroframes to improve error rate performance.

TABLE 8 Example of HARQ-ACK transmission timing for an n + 2 ruleConfiguration 0 1 2 3 4 5 6 0 UL 2 — — — — — — 1 UL 2 UL 3 — — — — — 2UL 3 UL 4 UL 5 — — — — 3 UL 4 UL 5 UL 6 UL 6 — — — 4 UL 5 UL 5 UL 6 UL 6UL 6 — — 5 UL 6 UL 6 UL 6 UL 7 UL 7 UL 7 — 6 UL 7 UL 7 UL 7 UL 7 UL 7 UL7 *

A baseline rule for HARQ-ACK transmission is shown using python codewhere delta=2 (the “2” in n+2 rule), cfg is uplink-downlinkconfiguration, maxum is the number of microframes in a subframe, and dlis the microframe of data transmission. This routine can provide aninitial configuration after which improvements for reducing latency,bundling/multiplexing, and performance can be added. In an embodiment,the following code can be used for n+3, n+4, etc. by changing deltaappropriately.

def check_(computed, maxum):  flag = 2*maxum  if computed < maxum:  return computed  return flag def generate(delta, cfg, dl, maxum): offset = cfg − dl  if offset < 0   return no_d1  if offset==0:  computed = cfg+delta   return check_(computed, maxum)  ifoffset<delta:   computed = delta + min(cfg−1, dl)   returncheck_(computed, maxum)  if offset==delta:   computed = dl+delta+1  return check_(computed, maxum)  if offset>delta:   computed = cfg+1  return check_(computed, maxum)   return illegal_case

TDD implementations can cause different latencies. There is apresumption that an eNB needs at least 1 microframe to process HARQ-ACKbits and to schedule a downlink transmission. For example, if HARQ-ACKbits are transmitted by a UE in microframe 6, the eNB would need aportion of microframe 7 to process those HARQ-ACK bits, to determinewhat to transmit in microframe 0, and to prepare that transmission.

TABLE 9 Example of latencies for transmission in subframe k, Dn is thenth microframe of the next subframe (k + 1). #m is the minimum delaywhere m is the multiple of 0.125 ms. Config- uration DL 0 DL 1 DL 2 DL 3DL 4 DL 5 DL 6 0 #8, D0 — — — — — — 1 #8, D0 #7, D0 — — — — — 2 #8, D0#7, D0 #6, D0 — — — — 3 #8, D0 #7, D0 #6, D0 #5, D1 — — — 4 #8, D0 #7,D0 #6, D0 #5, D1 #5, D1 — — 5 #8, D0 #7, D0 #6, D0 #5, D1 #5, D1 #4, D1— 6 #9, D1 #8, D1 #7, D1 #6, D1 #5, D1 #4, D1 *

FIG. 13 illustrates an embodiment of DL HARQ timing 1300. With respectto the n+2 rule, restricted uplink-downlink configurations, in oneexample of DL HARQ timing, the uplink-downlink configuration has atleast 2 DL microframes and at least 2 UL microframes, as shown in FIG.13. Table 10 captures some of the HARQ-ACK timing as well as the numberof HARQ processes. With uplink-downlink configuration 5, there can be 6HARQ processes (allowing one UE to receive packets in 6 consecutivemicroframes). In this example, there is a minimum of 2 microframe delayfrom the reception of a downlink packet and the transmission of theHARQ-ACK bits. For certain uplink-downlink configurations (e.g., #4 and#5), the uplink microframe for transmitting HARQ-ACK bits corresponds toseveral downlink microframes (e.g., HARQ-ACK bits for microframe 0 (DL0) and microframe 1 (DL 1) are transmitted in microframe 5 (UL 5)). Inone example, when a UE receives multiple downlink packets in a subframeand the HARQ-ACK bits for those packets are scheduled for the sameuplink microframe, the UE may be configured by the eNB to concatenatethe HARQ-ACK bits for each of the downlink packets (multiplex) or toperform a logical AND of HARQ-ACK bits for each of the downlink packets(bundle), where a logical AND of two bits is 1 when both bits are equalto 1, 0 otherwise. Another possible rule for spatialmultiplexing/bundling is based on the microframe configuration. Ifuplink-downlink configuration x is used, then for data transmission oncertain microframes, spatial multiplexing/bundling is used.

TABLE 10 Uplink microframe timing for HARQ-ACK, n + 2 rule MaximumUplink- Number downlink of DL HARQ configuration processes DL 0 DL 1 DL2 DL 3 DL 4 DL 5 1 2 UL 2 UL 3 — — — — 2 3 UL 3 UL 4 UL 5 — — — 3 4 UL 4UL 5 UL 6 UL 7 — — 4 5 UL 5 UL 5 UL 6 UL 6 UL 7 — 5 6 UL 6 UL 6 UL 6 UL7 UL 7 UL 7

Another possibility is to add a field in the DCI to indicate on whichsubframe the packet is to be acknowledged. One bit could indicate if apre-determined subframe is to be used for sending the ACK/NAK. Dependingon the value of this bit, the UE knows where to send the ACK/NAK:

If bit value is ‘0’, the UE uses a pre-defined implicit rule (e.g., n,n+2) for sending the ACK, and

If bit value is ‘1’, the UE uses a pre-defined microframe for sendingthe ACK (e.g., microframe #7).

Note that instead of being a specific value, the bit could be toggled.The pre-defined microframe could be obtained through pre-configuration,configuration through RRC signaling, physical layer signaling (DCI),etc.

If the UE is configured by the eNB to concatenate the HARQ-ACK bits foreach of the downlink packets (multiplex) or to perform a logical AND ofHARQ-ACK bits for each of the downlink packets (bundle), the UE willalways use multiplexing or bundling of the HARQ-ACK bits.

If the UE is not configured by the eNB to use multiplexing or bundling,in each microframe the eNB can signal multiplexing or bundling to theUE. One additional bit can be used in the DCI to indicate to usemultiplexing or bundling:

If bit value is ‘0’, the UE concatenates the HARQ-ACK bits for each ofthe downlink packets, and

If bit value is ‘1’, the UE performs a logical AND of HARQ-ACK bits foreach of the downlink packets.

An alternative is for the eNB to send the microframe index when theACK/NAK is sent. Note that this alternative has higher overhead thanone-bit indicators. The index can be for the same subframe or it can bein the next subframe. Example, consider the case if DL packet is inmicroframe 6. In an embodiment, the ACK is sent in the next subframe.

FIG. 14 and FIG. 15 show UE and eNB example operations for variableuplink-downlink configurations, respectively.

FIG. 14 illustrates an embodiment method 1400 in an eNB for HARQ-ACKflow. For the eNB operation in FIG. 14, the method 1400 begins at block1402 where the eNB transmits the uplink-downlink configuration for thecurrent subframe in microframe 0. In one example, the transmission canuse a waveform or be DCI-based. At block 1404, in microframe n, the eNBtransmits the PDSCH. Microframe n is in the same subframe as microframe0 and is a downlink (or special) microframe. Typically the (E)PDCCHcorresponding to the PDSCH is transmitted in the same microframe as thePDSCH. In some instances, the (E)PDCCH can be transmitted in an earliermicroframe. For semi-persistent scheduling, there may be no (E)PDCCHcorresponding to the PDSCH. In block 1406, based on the timing rules(e.g., n+2), the uplink-downlink configuration for the current subframe,and microframe n, the eNB determines which microframe (microframe m) theHARQ-ACK bits will be transmitted by the UE. Note the uplink-downlinkconfiguration for the next subframe may also be considered indetermining microframe m. The eNB may also make the determination basedon whether there are more PDSCH transmissions to that UE in the samesubframe. This can determine whether HARQ-ACK bits are bundled ormultiplexed. Another consideration is whether TTI bundling is used forACK/NAK information. TTI bundling is the repetition of transmission ofACK/NAK information by a UE and can improve coverage by allowing the eNBto combine several ACK/NAK information (to boost SNR). Note that the eNBmay make the determination of microframe m before it transmits the PDSCHin microframe n. The eNB may have to change the DCI fields of the(E)PDCCH accordingly so that the UE knows when to transmit the HARQ-ACKbits corresponding to the PDSCH in microframe n. At block 1408, inmicroframe m (or multiple microframes if TTI bundling is used), the eNBreceives the ACK/NAK information containing the HARQ-ACK bits for thetransmission of PDSCH in microframe n, after which, the method 1400ends.

FIG. 15 illustrates an embodiment method 1500 in a UE for HARQ-ACK flow.For the UE operation in FIG. 15, at block 1502, the UE receives theuplink-downlink configuration for the current subframe in microframe 0.In one example, the uplink-downlink configuration can be conveyed usinga waveform or by DCI. At block 1504, in microframe n, the UE receivesthe PDSCH. At block 1506, the UE will generate HARQ-ACK bits afterattempting to decode the PDSCH. For example, a HARQ-ACK bit value of “1”can indicate successful reception of the PDSCH. A “0” can indicate otherinformation (e.g., unsuccessful decoding, missed (E)PDCCH). Typically,the (E)PDCCH corresponding to the PDSCH is received in the samemicroframe as the PDSCH. In some instances, the (E)PDCCH can be receivedin an earlier microframe. At block 1508, based on the timing rules(e.g., n+2), the uplink-downlink configuration for the current subframe,and microframe n, the UE determines which microframe (microframe m) theACK/NAK information containing the HARQ-ACK bits will be transmitted.Note the uplink-downlink configuration for the next subframe may also beconsidered in determining microframe m. The UE may have to use bundlingor multiplexing of HARQ-ACK bits when there are multiple HARQ-ACK bits(corresponding to different PDSCH). Another consideration is TTIbundling. Note that the (E)PDCCH may contain fields indicating whenand/or which resources are used for ACK/NAK information transmission. Atblock 1510, in microframe m (or multiple microframes if TTI bundling isused), the UE transmits the ACK/NAK information containing the HARQ-ACKbits for the reception of PDSCH in microframe n, after which, the method1500 may end.

FIG. 16 illustrates an embodiment of UL HARQ timing 1600. With respectto UL HARQ, in one example the uplink-downlink configuration has atleast 2 DL microframes and at least 2 UL microframes, as shown in FIG.16. Table 11 captures some of the HARQ-ACK timing as well as the numberof HARQ processes. With uplink-downlink configuration 5, there can be 2processes (allowing one UE to transmit packets in 6 consecutivemicroframes). In this example, there is a minimum of 2 microframe delayfrom the transmission of an uplink packet and the rescheduling for ULgrants (transmission of HARQ-ACK bits by the eNB can be indicated by theDCI for UL grants).

TABLE 11 Downlink microframe timing for HARQ-ACK Maximum Uplink- Numberdownlink of DL HARQ configuration processes UL 2 UL 3 UL 4 UL 5 UL 6 UL7 1 6 — — — — DL 0 DL 1 2 5 — — — DL 0 DL 0 DL 1 3 4 — — DL 0 DL 0 DL 0DL 1 4 3 — DL 0 DL 0 DL 0 DL 0 DL 1 5 2 DL 0 DL 0 DL 0 DL 0 DL 0 DL 1

FIG. 17 illustrates a block diagram of an embodiment processing system1700 for performing methods described herein, which may be installed ina host device. As shown, the processing system 1700 includes a processor1704, a memory 1706, and interfaces 1710-1714, which may (or may not) bearranged as shown in FIG. 17. The processor 1704 may be any component orcollection of components adapted to perform computations and/or otherprocessing related tasks, and the memory 1706 may be any component orcollection of components adapted to store programming and/orinstructions for execution by the processor 1704. In an embodiment, thememory 1706 includes a non-transitory computer readable medium. Theinterfaces 1710, 1712, 1714 may be any component or collection ofcomponents that allow the processing system 1700 to communicate withother devices/components and/or a user. For example, one or more of theinterfaces 1710, 1712, 1714 may be adapted to communicate data, control,or management messages from the processor 1704 to applications installedon the host device and/or a remote device. As another example, one ormore of the interfaces 1710, 1712, 1714 may be adapted to allow a useror user device (e.g., personal computer (PC), etc.) tointeract/communicate with the processing system 1700. The processingsystem 1700 may include additional components not depicted in FIG. 17,such as long term storage (e.g., non-volatile memory, etc.).

In some embodiments, the processing system 1700 is included in a networkdevice that is accessing, or part otherwise of, a telecommunicationsnetwork. In one example, the processing system 1700 is in a network-sidedevice in a wireless or wireline telecommunications network, such as abase station, a relay station, a scheduler, a controller, a gateway, arouter, an applications server, or any other device in thetelecommunications network. In other embodiments, the processing system1700 is in a user-side device accessing a wireless or wirelinetelecommunications network, such as a mobile station, a user equipment(UE), a personal computer (PC), a tablet, a wearable communicationsdevice (e.g., a smartwatch, etc.), or any other device adapted to accessa telecommunications network.

In some embodiments, one or more of the interfaces 1710, 1712, 1714connects the processing system 1700 to a transceiver adapted to transmitand receive signaling over the telecommunications network.

FIG. 18 illustrates a block diagram of a transceiver 1800 adapted totransmit and receive signaling over a telecommunications network. Thetransceiver 1800 may be installed in a host device. As shown, thetransceiver 1800 includes a network-side interface 1802, a coupler 1804,a transmitter 1806, a receiver 1808, a signal processor 1810, and adevice-side interface 1812. The network-side interface 1802 may includeany component or collection of components adapted to transmit or receivesignaling over a wireless or wireline telecommunications network. Thecoupler 1804 may include any component or collection of componentsadapted to facilitate bi-directional communication over the network-sideinterface 1802. The transmitter 1806 may include any component orcollection of components (e.g., up-converter, power amplifier, etc.)adapted to convert a baseband signal into a modulated carrier signalsuitable for transmission over the network-side interface 1802. Thereceiver 1808 may include any component or collection of components(e.g., down-converter, low noise amplifier, etc.) adapted to convert acarrier signal received over the network-side interface 1802 into abaseband signal. The signal processor 1810 may include any component orcollection of components adapted to convert a baseband signal into adata signal suitable for communication over the device-side interface(s)1812, or vice-versa. The device-side interface(s) 1812 may include anycomponent or collection of components adapted to communicatedata-signals between the signal processor 1810 and components within thehost device (e.g., the processing system 1700, local area network (LAN)ports, etc.).

The transceiver 1800 may transmit and receive signaling over any type ofcommunications medium. In some embodiments, the transceiver 1800transmits and receives signaling over a wireless medium. For example,the transceiver 1800 may be a wireless transceiver adapted tocommunicate in accordance with a wireless telecommunications protocol,such as a cellular protocol (e.g., long-term evolution (LTE), etc.), awireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or anyother type of wireless protocol (e.g., Bluetooth, near fieldcommunication (NFC), etc.). In such embodiments, the network-sideinterface 1802 includes one or more antenna/radiating elements. Forexample, the network-side interface 1802 may include a single antenna,multiple separate antennas, or a multi-antenna array configured formulti-layer communication, e.g., single input multiple output (SIMO),multiple input single output (MISO), multiple input multiple output(MIMO), etc. In other embodiments, the transceiver 1800 transmits andreceives signaling over a wireline medium, e.g., twisted-pair cable,coaxial cable, optical fiber, etc. Specific processing systems and/ortransceivers may utilize all of the components shown, or only a subsetof the components, and levels of integration may vary from device todevice.

FIG. 19 illustrates an embodiment network 1900 for communicating data inwhich the disclosed methods and systems may be implemented. The network1900 includes an access point (AP) 1910 having a coverage area 1912, aplurality of stations (STAs) 1920, and a backhaul network 1930. In anembodiment, the AP may be implemented as transceiver 1800 shown in FIG.18. In an embodiment, the STAs 1920 may be implemented as, for example,processing system 1700 shown in FIG. 17. As used herein, the term AP mayalso be referred to as a TP and the two terms may be usedinterchangeably throughout this disclosure. The AP 1910 may include anycomponent capable of providing wireless access by, inter alia,establishing uplink (dashed line) and/or downlink (dotted line)connections with the STAs 1920. The STAs 1920 may include any componentcapable of establishing a wireless connection with the AP 1910. Examplesof STAs 1920 include mobile phones, tablet computers, and laptopcomputers. The backhaul network 1930 may be any component or collectionof components that allow data to be exchanged between the AP 1910 and aremote end (not shown). In some embodiments, the network 1900 mayinclude various other wireless devices, such as relays, femtocells, etc.

An embodiment method in a communications controller for transmitting apacket to a wireless device includes signaling, by the communicationscontroller, an uplink/downlink (UL/DL) configuration to the wirelessdevice, wherein the UL/DL configuration indicates a quantity of uplinkmicroframes in a group of microframes, wherein each subframe includes aplurality of microframes, and wherein the group of microframes includesa consecutive sequence downlink microframes and a consecutive sequenceof uplink microframes. The method also includes transmitting, by thecommunications controller, the packet to the wireless device in onedownlink microframe of the consecutive sequence of downlink microframes.The method further includes receiving, by the communications controller,an acknowledgement of the packet in an uplink microframe, wherein theuplink microframe is determined in accordance with the one downlinkmicroframe and the uplink-downlink configuration, and wherein theacknowledgement is received in a same subframe as a subframe utilizedfor transmitting the packet to the wireless device.

In an embodiment, the consecutive sequence of downlink microframesincludes a special microframe, and wherein the special microframeincludes at least one downlink symbol and a guard period. In anembodiment, the uplink microframes are further determined in accordancewith a next uplink-downlink configuration of a next group ofmicroframes. In an embodiment, the quantity of uplink microframes isrelated to the consecutive sequence of uplink microframes. In anembodiment, a subframe is divided into eight microframes, wherein Kfirst microframes are UL. In an embodiment, a plurality of subframescomprise a supermicroframe, wherein a K first microframes in a firstsubframe are DL microframes and a first microframe in each of thesubsequent subframes are a DL microframe or an UL microframe. In anembodiment, the method also includes signaling the UL/DL configurationusing a physical control format indicator channel (PCFICH)-like channel.In an embodiment, signaling the UL/DL configuration using a physicalcontrol format indicator channel (PCFICH)-like channel includes sendingthe PCFICH-like channel on at least one reserved resource element (RE)in a first microframe of a first subframe. In an embodiment, the firstmicroframe includes microframe 0 and the first subframe includessubframe 0. In an embodiment, the method includes explicitly signaling asubframe in which to send an acknowledgement/negative acknowledgement(ACK/NAK). In an embodiment, the explicit signaling includes one bitindicating whether to send the ACK/NACK using an implicit rule or apre-determined microframe.

An embodiment communications controller includes a processor and anon-transitory computer readable storage medium storing programming forexecution by the processor. The programming includes instructions forsignaling an uplink/downlink (UL/DL) configuration to the wirelessdevice, wherein the UL/DL configuration indicates a quantity of uplinkmicroframes in a group of microframes. Each subframe includes aplurality of microframes. The group of microframes includes aconsecutive sequence downlink microframes and a consecutive sequence ofuplink microframes. The programming also includes instructions fortransmitting the packet to the wireless device in one downlinkmicroframe of the consecutive sequence of downlink microframes. Theprogramming further includes instructions for receiving anacknowledgement of the packet in an uplink microframe. The uplinkmicroframe is determined in accordance with the one downlink microframeand the uplink-downlink configuration. The acknowledgement is receivedin a same subframe as a subframe utilized for transmitting the packet tothe wireless device.

In an embodiment, the consecutive sequence of downlink microframesincludes a special microframe, and wherein the special microframeincludes at least one downlink symbol and a guard period. In anembodiment, the uplink microframes are further determined in accordancewith a next uplink-downlink configuration of a next group ofmicroframes. In an embodiment, the quantity of uplink microframes isrelated to the consecutive sequence of uplink microframes. In anembodiment, a subframe is divided into eight microframes, wherein Kfirst microframes are UL. In an embodiment, a plurality of subframescomprise a supermicroframe, wherein a K first microframes in a firstsubframe are DL microframes and a first microframe in each of thesubsequent subframes are a DL microframe or an UL microframe. In anembodiment, the programming further includes instructions for signalingthe UL/DL configuration using a physical control format indicatorchannel (PCFICH)-like channel. In an embodiment, signaling the UL/DLconfiguration using a physical control format indicator channel(PCFICH)-like channel includes sending the PCFICH-like channel on atleast one reserved resource element (RE) in a first microframe of afirst subframe. In an embodiment, the first microframe includesmicroframe 0 and the first subframe includes subframe 0. In anembodiment, the programming further includes instructions for explicitlysignaling a subframe in which to send an acknowledgement/negativeacknowledgement (ACK/NAK).

An embodiment method in a wireless device for communicating with acommunications controller includes receiving, by the wireless device, anuplink/downlink (UL/DL) configuration from the communicationscontroller. The UL/DL configuration indicates a quantity of uplinkmicroframes in a group of microframes. Each subframe includes aplurality of microframes. The group of microframes includes aconsecutive sequence downlink microframes and a consecutive sequence ofuplink microframes. The method also includes receiving, by the wirelessdevice, a packet from the communications controller in one downlinkmicroframe of the consecutive sequence of downlink microframes. Themethod further includes transmitting, by the wireless device, anacknowledgement of the packet in an uplink microframe. The uplinkmicroframe is determined in accordance with the one downlink microframeand the uplink-downlink configuration. The acknowledgement istransmitted in a same subframe as a subframe utilized for receiving thepacket from the communications controller. In an embodiment, theconsecutive sequence of downlink microframes includes a specialmicroframe, and wherein the special microframe includes at least onedownlink symbol and a guard period. In an embodiment, the uplinkmicroframes are further determined in accordance with a nextuplink-downlink configuration of a next group of microframes. In anembodiment, a subframe is divided into eight microframes, wherein Kfirst microframes are UL. In an embodiment, a plurality of subframescomprise a supermicroframe, wherein a K first microframes in a firstsubframe are DL microframes and a first microframe in each of thesubsequent subframes are a DL microframe or an UL microframe.

An embodiment wireless device includes a processor and a non-transitorycomputer readable storage medium storing programming for execution bythe processor. The programming includes instructions for receiving anuplink/downlink (UL/DL) configuration from the communicationscontroller. The UL/DL configuration indicates a quantity of uplinkmicroframes in a group of microframes. Each subframe includes aplurality of microframes. The group of microframes includes aconsecutive sequence of downlink microframes and a consecutive sequenceof uplink microframes. The programming also includes instructions forreceiving a packet from the communications controller in one downlinkmicroframe of the consecutive sequence of downlink microframes. Theprogramming also includes transmitting an acknowledgement of the packetin an uplink microframe. The uplink microframe is determined inaccordance with the one downlink microframe and the uplink-downlinkconfiguration. The acknowledgement is transmitted in a same subframe asa subframe utilized for receiving the packet from the communicationscontroller. In an embodiment, the consecutive sequence of downlinkmicroframes includes a special microframe. The special microframeincludes at least one downlink symbol and a guard period. In anembodiment, the uplink microframes are further determined in accordancewith a next uplink-downlink configuration of a next group ofmicroframes. In an embodiment, a subframe is divided into eightmicroframes. The K first microframes are UL. In an embodiment, aplurality of subframes comprise a supermicroframe, wherein a K firstmicroframes in a first subframe are DL microframes and a firstmicroframe in each of the subsequent subframes are a DL microframe or anUL microframe.

It should be appreciated that one or more steps of the embodimentmethods provided herein may be performed by corresponding units ormodules. For example, a signal or packet may be transmitted by atransmitting unit or a transmitting module. A signal or packet may bereceived by a receiving unit or a receiving module. A signal or packetmay be processed by a processing unit or a processing module. Therespective units/modules may be hardware, software, or a combinationthereof. For instance, one or more of the units/modules may be anintegrated circuit, such as field programmable gate arrays (FPGAs) orapplication-specific integrated circuits (ASICs).

The following references are related to subject matter of the presentapplication. Each of these references is incorporated herein byreference in its entirety:

-   -   3GPP TS 36.211 version 10.0.0, Release 10, “LTE; Evolved        Universal Terrestrial Radio Access (E-UTRA); Physical channels        and modulation,” (2011-01).

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

What is claimed is:
 1. A method comprising: signaling, by acommunications controller, a higher layer signal indicating a pluralityof downlink frames and a plurality of uplink frames; signaling, by thecommunications controller, a first downlink control information (DCI)message that includes a first indicator for a portion of a downlinkframe, in the plurality of downlink frames, for transmitting a packet toa wireless device and a second indicator for a portion of an uplinkframe, in the plurality of uplink frames, for receiving anacknowledgement associated with the packet from the wireless device; andreceiving, by the communications controller, the acknowledgement in theportion of the uplink frame.
 2. The method of claim 1, wherein a specialframe follows the plurality of downlink frames and precedes theplurality of uplink frames, the special frame comprises at least onedownlink symbol and a guard period.
 3. The method of claim 1, whereinthe DCI is signaled on a physical downlink control channel (PDCCH)located in a common search space being monitored by the wireless device.4. The method of claim 1, wherein the downlink frame comprises a cyclicprefix, and wherein a duration of the cyclic prefix is based on asampling rate, a subcarrier spacing, or a number of frames in asubframe.
 5. The method of claim 1, wherein the acknowledgement includesa separate acknowledgement indications for each of a plurality ofpackets transmitted over the plurality of downlink frames.
 6. The methodof claim 1, further comprising: signaling a second DCI message thatincludes a third indicator for a portion of a second uplink frame, inthe plurality of uplink frames, for receiving an uplink datatransmission from the wireless device.
 7. The method of claim 1, whereinthe portion of the downlink frame consists of a number of symbols eachof which having a symbol duration corresponding to a subcarrier spacingof the downlink frame.
 8. The method of claim 1, wherein the portion ofthe downlink frame comprises a duration that is 0.125 ms or a multipleof 0.125 ms.
 9. The method of claim 1, wherein the portion of the uplinkframe consists of a number of symbols each of which having a symbolduration corresponding to a subcarrier spacing of the uplink frame. 10.The method of claim 1, wherein the portion of the uplink frame comprisesa duration that is 0.125 ms or a multiple of 0.125 ms.
 11. Acommunications controller comprising: a non-transitory memory storagecomprising instructions; and a processor in communication with thenon-transitory memory storage, wherein the processor executes theinstructions to : signal a higher layer signal indicating a plurality ofdownlink frames and a plurality of uplink frames; signal a firstdownlink control information (DCI) message that includes a firstindicator for a portion of a downlink frame, in the plurality ofdownlink frames, for transmitting a packet to a wireless device and asecond indicator for a portion of an uplink frame, in the plurality ofuplink frames, for receiving an acknowledgement associated with thepacket from the wireless device; and receive the acknowledgement in theportion of the uplink frame.
 12. The communications controller of claim11, wherein a special frame follows the plurality of downlink frames andprecedes the plurality of uplink frames, the special frame comprises atleast one downlink symbol and a guard period.
 13. The communicationscontroller of claim 11, wherein the DCI is signaled on a physicaldownlink control channel (PDCCH) located in a common search space beingmonitored by the wireless device.
 14. The communications controller ofclaim 11, wherein the portion of the downlink frame comprises a cyclicprefix, and wherein a duration of the cyclic prefix is based on asampling rate, a subcarrier spacing, or a number of frames in asubframe.
 15. The communications controller of claim 11, wherein theacknowledgement includes a separate acknowledgement indications for eachof a plurality of packets transmitted over the plurality of downlinkframes.
 16. The communications controller of claim 11, wherein theprogramming further includes instructions to: signal a second DCImessage that includes a third indicator for a portion of a second uplinkframe, in the plurality of uplink frames, for receiving an uplink datatransmission from the wireless device.
 17. A method comprising:receiving, by a wireless device, a higher layer signal indicating aplurality of downlink frames and a plurality of uplink frames;receiving, by the wireless device, a first downlink control information(DCI) message that includes a first indicator for a portion of adownlink frame, in the plurality of downlink frames, for receiving awireless packet from a communications controller and a second indicatorfor a portion of an uplink frame, in the plurality of uplink frames, fortransmitting an acknowledgement associated with the packet to thecommunications controller; and transmitting, by the wireless device, theacknowledgement in the portion of the uplink frame.
 18. The method ofclaim 17, wherein a special frame follows the plurality of downlinkframes and precedes the plurality of uplink frames, the special framecomprises at least one downlink symbol and a guard period.
 19. Themethod of claim 17, wherein the DCI is signaled on a physical downlinkcontrol channel (PDCCH) located in a common search space being monitoredby the wireless device.
 20. The method of claim 17, wherein the portionof the downlink frame comprises a cyclic prefix, and wherein a durationof the cyclic prefix is based on a sampling rate, a subcarrier spacing,or a number of frames in a subframe.
 21. The method of claim 17, whereinthe acknowledgement includes a separate acknowledgement indications foreach of a plurality of packets transmitted over the plurality ofdownlink frames.
 22. The method of claim 17, further comprising:receiving a second DCI message that includes a third indicator for aportion of a second uplink frame, in the plurality of uplink frames, fortransmitting an uplink data transmission to the communicationscontroller.
 23. The method of claim 17, wherein the portion of thedownlink frame consists of a number of symbols each of which having asymbol duration corresponding to a subcarrier spacing of the downlinkframe.
 24. The method of claim 17, wherein the portion of the downlinkframe comprises a duration that is 0.125 ms or a multiple of 0.125 ms.25. The method of claim 17, wherein the portion of the uplink frameconsists of a number of symbols each of which having a symbol durationcorresponding to a subcarrier spacing of the uplink frame.
 26. Themethod of claim 17, wherein the portion of the uplink frame comprises aduration that is 0.125 ms or a multiple of 0.125 ms.
 27. A wirelessdevice comprising: a non-transitory memory storage comprisinginstructions; and a processor in communication with the non-transitorymemory storage, wherein the processor executes the instructions to:receive a higher layer signal that indicates a plurality of downlinkframes and a plurality of uplink frames; receive a first downlinkcontrol information (DCI) message that includes a first indicator for aportion of a downlink frame, in the plurality of downlink frames, forreceiving a wireless packet from a communications controller and asecond indicator for a portion of an uplink frame, in the plurality ofuplink frames, for transmitting an acknowledgement associated with thepacket to the communications controller; and transmit theacknowledgement in the portion of the uplink frame.
 28. The wirelessdevice of claim 27, wherein a special frame follows the plurality ofdownlink frames and precedes the plurality of uplink frames, the specialframe comprises at least one downlink symbol and a guard period.
 29. Thewireless device of claim 27, wherein the DCI is signaled on a physicaldownlink control channel (PDCCH) located in a common search space beingmonitored by the wireless device.
 30. The wireless device of claim 27,wherein the downlink frame comprises a cyclic prefix, and wherein aduration of the cyclic prefix is based on a sampling rate, a subcarrierspacing, or a number of frames in a subframe.
 31. The wireless device ofclaim 27, wherein the acknowledgement includes a separateacknowledgement indications for each of a plurality of packetstransmitted over the plurality of downlink frames.
 32. The wirelessdevice of claim 27, wherein the programming further includesinstructions to: receive a second DCI message that includes a thirdindicator for a portion of a second uplink frame, in the plurality ofuplink frames, for transmitting an uplink data transmission to thecommunications controller.